A unique new polyoma virus strain which accumulates capsid polypeptide in the cytoplasm of permissive cells has recently been described in this laboratory. This strain has now been shown to produce 2-4 fold more capsid polypeptide and 2-fold more virus-specific, poly(A)-containing RNA than a comparable wild-type strain. Studies to define the mechanism by which regulation of transcription or post- transcriptional processing of viral RNA is altered will include measurement of the synthesis of virus specific RNA and its turnover, analysis of the RNA polymerase that transcribe viral and host cell DNA as well as the poly(A) polymerase that polyadenylates mRNA. A hamster tumor cell line transformed by this variant has been found to have a markedly diminished rate of processing of small, newly replicated DNA fragments to form high MW DNA. Experiments to define the mechanism of the altered rate of processing of this DNA are proposed and the role of the variant virus in the etiology of the abnormality will be studied. These studies are designed to provide information on the mechanism by which the genetic information of a small oncogenic DNA virus is regulated in a permissive host cell and how certain vital host cell functions, such as DNA synthesis, are modulated by that virus during the process of oncogenesis.